Pilot deviated from assigned altitude.

Attributes
ACN	88181
Time
Date	198805
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : bfl
State Reference	CA
Altitude	msl bound lower : 3000 msl bound upper : 10000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bfl
Operator	common carrier : air taxi
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	oversight : pic
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 1535 flight time type : 150
ASRS Report	88181
Person 2
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot inflight encounter : weather non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : returned to intended course or assigned course flight crew : overcame equipment problem flight crew : declared emergency
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On an IFR flight plan from bur to concord, I encountered light icing through 8700' MSL. Icing stopped passing -8 degrees C at 8700' MSL. At 10000' MSL, 8 mi southeast of gorman VOR, icing started again at - 10 degrees C. Pitot heat and propeller heat was on. I requested lower as soon as possible from la center. They said expect lower 7 mi past gorman. I acknowledged and maintained 10000' to gorman. 2 mi past gorman the nose pitched up 5-10 degrees. Full forward yoke maintained 5-10 degrees nose up. Last airspeed indication was 100 and decreasing. Airspeed went to 0, ball and turn needle were erratic due to turbulence. Vsi varied between +500 to -2000 FPM. Altimeter would hold, then jump 500, then drop 500. I announced an emergency and that I was descending. Due to varying instrument indications and lack of control response, I announced I may have been in a spin. I switched on the alternate static source, stabilized attitude gyro, ball and dg. All indication became normal except airspeed and I requested a ground speed check from center. They showed 140 gndspd and estimated 110 KIAS. I stabilized and was switched to bfl approach. Bfl cleared me to 6000'. I cancelled the emergency, cancelled IFR and requested VFR flight following and descent to 4500'. I completed clt checks and requested a VFR descent to 2500'. I continued radar flight following and control checks. All systems were normal and I notified company of my proposed arrival time at concord and completed the run.

Original NASA ASRS Text

Title: PLT DEVIATED FROM ASSIGNED ALT.

Narrative: ON AN IFR FLT PLAN FROM BUR TO CONCORD, I ENCOUNTERED LIGHT ICING THROUGH 8700' MSL. ICING STOPPED PASSING -8 DEGS C AT 8700' MSL. AT 10000' MSL, 8 MI SE OF GORMAN VOR, ICING STARTED AGAIN AT - 10 DEGS C. PITOT HEAT AND PROP HEAT WAS ON. I REQUESTED LOWER ASAP FROM LA CENTER. THEY SAID EXPECT LOWER 7 MI PAST GORMAN. I ACKNOWLEDGED AND MAINTAINED 10000' TO GORMAN. 2 MI PAST GORMAN THE NOSE PITCHED UP 5-10 DEGS. FULL FORWARD YOKE MAINTAINED 5-10 DEGS NOSE UP. LAST AIRSPD INDICATION WAS 100 AND DECREASING. AIRSPD WENT TO 0, BALL AND TURN NEEDLE WERE ERRATIC DUE TO TURB. VSI VARIED BTWN +500 TO -2000 FPM. ALTIMETER WOULD HOLD, THEN JUMP 500, THEN DROP 500. I ANNOUNCED AN EMER AND THAT I WAS DSNDING. DUE TO VARYING INSTRUMENT INDICATIONS AND LACK OF CTL RESPONSE, I ANNOUNCED I MAY HAVE BEEN IN A SPIN. I SWITCHED ON THE ALTERNATE STATIC SOURCE, STABILIZED ATTITUDE GYRO, BALL AND DG. ALL INDICATION BECAME NORMAL EXCEPT AIRSPD AND I REQUESTED A GND SPD CHK FROM CENTER. THEY SHOWED 140 GNDSPD AND ESTIMATED 110 KIAS. I STABILIZED AND WAS SWITCHED TO BFL APCH. BFL CLRED ME TO 6000'. I CANCELLED THE EMER, CANCELLED IFR AND REQUESTED VFR FLT FOLLOWING AND DSCNT TO 4500'. I COMPLETED CLT CHKS AND REQUESTED A VFR DSCNT TO 2500'. I CONTINUED RADAR FLT FOLLOWING AND CTL CHKS. ALL SYSTEMS WERE NORMAL AND I NOTIFIED COMPANY OF MY PROPOSED ARR TIME AT CONCORD AND COMPLETED THE RUN.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.